There is one type of light emitting element called a frame laser. The frame laser is built by fixing a pair of lead frames formed out of a conductive material in a case formed out of an insulating material, with a semiconductor laser element fixed on one of the lead frames and connected by wire bonding to the other lead frame. Japanese Patent Application Laid-open No. H3-188692 discloses an example of a frame laser. Japanese Patent Application Laid-open No. 2003-152228 discloses an example of a light emitting element having a light emitting diode fixed on a lead frame.
Semiconductor lasers are widely used in writing data onto optical recording media or reading data therefrom. Due to a recent trend toward large capacity optical discs, the volume of data to be read and written has significantly increased, leading to demand for semiconductor lasers capable of exerting higher power.
The increase in the power exerted by a semiconductor laser results in an increase in the volume of heat generated. The increase in the temperature of a light emitting element causes problems such as deformation or discoloration of the case that encloses the semiconductor laser, requiring more effective measures against heat.
One common measure against heat is to increase the area of the lead frame so as to improve heat dissipation. Simply increasing the area of the lead frame, however, may result in the enlarged portion protruding out of the case. The portion protruding out of the case requires insulation, leading to an increase in the number of processes, which in turn leads to higher cost. Enclosing the entire lead frame including the enlarged portion inside the case so as to omit the need for insulation leads to overall upsizing, which goes against the downsizing trend of components.